Kostas,
The rules of the PMP exam are such that PMI clearly "forbids" anyone taking he exam to talk about the details of their experience. This means that we are not allowed to ask any specific questions either. That much said: we have not made any qualitative comparison of the questions in the PM Exam Simulator vs. the questions on the exam.
However... we know from student's anecdotes (what they say in testimonials and "thank you" emails) the following three items:
1) The style of the questions in the simulator are very similar to the questions on the real exam.
2) The questions on the simulator are almost "harder" than on the real exam
3) Simulator users felt well prepared to take their exam
"All of the above" and "none of the above" are question styles that are NOT on the real exam. And this is the one thing about our simulator that really bothers me, because it's my own fault. When we defined the original quality criteria, I forgot to include this into the "don'ts". So we ended up with quite a large number of this question style. We have eliminated about 80% of them and are still working on getting rid of them all. It takes time...
Until Next Time,
Cornelius Fichtner, PMP, CSM
President, OSP International LLC